Inductor drive means

ABSTRACT

A circuit providing a means of transferring and storing the energy from the collapsing field of a deenergized inductive load to a capacitor, and subsequently delivering this energy back to the inductive load to aid in its re-energization. A first circuit path is provided for transferring the energy from the inductive load to the capacitor, and a second circuit path is provided for transferring the energy from the capacitor to the inductive load, said second circuit path including a signal translating device, the conductivity of which is controlled by the charge on the capacitor at the time re-energization of the inductive load is initiated.

United States Patent [191 Puvogel Jan. 2, 1973 s41 INDUCTOR DRIVE MEANS3,337,748 8/1967 Rusch et al ..3l7/DlG. 4

[75] Inventor: John M. Puvogel, West Alexandria,

Ohio Primary Examiner-J. D. Miller Assistant Examiner-Harry E. Mosse,Jr. [73] Assignee: The National Cash Register Com- Atw j Cavender et 1pany, Dayton, Ohio 221 Filed: Aug. 2, 1971 ABSTRACT 21 Appl' 1 3 052 Acircuit providing a means of transferring and storing the energy fromthe collapsing field of a deenergized inductive load to a capacitor, andsubsequently [52] "317/1485 317/151 317/DIG- delivering this energy backto the inductive load to aid 5 l I t CI 317mm 6 in its re-energization.A first circuit path is provided [58] Flt id ..H0lh 47/22 fortransferring the energy from the inductive load to 1 o earch "317/123,the capacitor, and a second circuit path is provided 317mm 318/696 fortransferring the energy from the capacitor to the R f d inductive load,said second circuit path including a e erences signal translatingdevice, the conductivity of which is UNITED STATES PATENTS controlled bythe charge on the capacitor at the time re-energlzation of the inductiveload is initiated. 3,467,894 9/1969 Blume ..3l7/l48.5 B 2,907,92910/1959 Lawson ..317/DIG. 6 10 Claims, 2 Drawing Figures PATENTEDJAN 2ma sum 1 0r 2 FIG.

mvsmon JOHN M. PUVOGEL HIS ATTORNEYS PATENTEDJAII 2 ma CURRENT IINDUCTIVE LOAD I2 I v V, NEGATIVE TERM. L+ OLT CAPACITOR 32 I l I lSHEET 2 [If 2 TRANSISTOR 24 OFF Q'X g INDUCTIVE LOAD INDUCTLOAD v,COLLECTOR TRANSISTOR 24 DEENERG'ZED ENERGIZED,

V, POSITIVE TERM. I CAPACITOR 32 l V,CAPAC|TOR 32 I GATE CURRENT IRECTIFIER 4o l I II I I II I 'l I I I l I CURRENT CAPACITOR 32COMPARISON WITH IN DUCTOR CURRENT OF USUAL ACTIVATION CUR R E NT RAPIDCURRENT RISE DUE TO CONSERVED ENERGY USUAL CURRENT INVENTOR JOHN M.PUVOGE L HIS ATTORNEYS ruuuc'ron DRIVE MEANS BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates to a circuitfor energizing an inductive load. In this circuit, energy produced whenthe inductive load is deenergized is stored and applied to the inductiveload at its next energization, in order to enhance the speed of suchenergization, and to reduce the energy required.

2. Description of the Prior Art Energizing circuits for energizinginductive loads are well known. In U.S. Pat. No. 3,379,946, issued Apr.23, 1968, on the application of Jacques Johannes Hendrik Croymans, astepping motor having a single energizing winding is provided with apulsing circuit having a single-pole double-throw switch whichautomatically returns to rest, and which, in first position, pulses theenergizing winding and charges a capacitor, and, in second position,allows the capacitor to discharge through the energizing winding. Thedouble pulsing allows the motor to take two steps for each switchingoperation.

In U.S. Pat. No. 3,402,334, issued Sept. 17, 1968, on the application ofGeorge C. Newton, J r., an energizing circuit is shown which is usefulfor driving complementary coils which are alternately energized. Energyresulting from the deenergization of one coil is applied directly to asecond coil for increasing the rate of current rise in this coil.

In FIGS. 7 and 8 of U.S. Pat. No. 3,444,447, issued May 13, 1969, on theapplication of Harold R. Newell, are shown circuit embodiments of adriving network which utilize the reverse voltage surge across onewinding when deenergized to enhance magnetic field buildup in acomplementary winding.

SUMMARY OF THE INVENTION This invention relates to an inductive loadenergizing circuit having the capability of storing the energy from thecollapsing field of a deenergized inductive load and subsequentlydelivering this energy back to the inductive load to aid in itsre-energization. Energization of the inductive load is controlled by aswitching means connected in series therewith in a first circuit pathextending across a power supply. A capacitor is included in the circuitfor the purpose of storing energy resulting from deenergization of theinductive load, and a second circuit path is provided, which includesthe inductive load and the capacitor.

Re-energization of the inductive load is accomplished by rendering thepreviously-mentioned switching means conducting, which also causes thecharge on the capacitor to produce a bias on the control electrode of asignal translating device included in a third circuit path which alsoincludes the inductive load, the capacitor, and the switching device.The signal-translating device is rendered conductive by said bias on itscontrol electrode, and enables the capacitor to discharge, thusproviding supplementary energy in said third path for re-energizing theinductive load.

The inductive load energizing circuit of the present invention thusprovides a means for storing the energy resulting from deenergization ofan inductive load, and subsequently utilizing this energy in there-energization of the inductive load. Advantages provided by this novelcircuit over a conventional energizing circuit include a lower powerinput requirement for rapid energization of an inductive load; reducedpower dissipation in the switching or regulating component; and reducedtime required for energization.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a diagram of an inductordrive circuit embodying the present invention.

FIG. 2 shows a series of wave forms associated with the operation of thecircuit of FIG. 1.

DETAILED DESCRIPTION In the circuit of FIG. 1, an inductive load 12 iscon nected at one end over a point 14 to a terminal 16, to which apositive source of potential V is connected. The inductive load 12 maycomprise one of the windings of a stepping motor, or may comprise anyother appropriate inductive load, such as a solenoid, for example. Atits other end, the inductive load 12 is connected over a point 18, adiode 20, which may be of the type 341, manufactured by WestinghouseElectric Corporation, of Pittsburgh, Pennsylvania, United States ofAmerica, and a point 22 to an energizing switch of any suitable type forcontrolling energization of the inductive load. In the illustratedembodiment, the point 22 is connected to the collector of an NPN- typetransistor 24, which may be of type 2N377 l manufactured by RCACorporation, of New York, New York, United States of America. Theemitter of the transistor 24 is connected to a base reference potentialshown in FIG. 1 as ground, and the base of said transistor is connectedto a terminal 26, to which may be applied a signal S E for energizingthe inductive load 12, as will subsequently be described. In FIG. 1, itmay be noted that the actual inductor drive circuitry is shown withinthe line 10.

From the point 14, a circuit branch extends over a diode 28, which maybe of type 341 manufactured by Westinghouse Electric Corporation, apoint 30, and a l5-micr0farad capacitor 32 to a point 34, from which onebranch connects the point 34 to the point 22, while a second branchextends over a 4,300-ohm resistor 36 to a terminal 38, to which isapplied a positive source of potential V which in the illustratedembodiment is 42 volts.

The point 18 is connected to the anode of a signal translating device40, which may be a silicon controlled rectifier of type C208,manufactured by General Electric Company, of New York, New York, UnitedStates of America. The cathode of said controlled rectifier is connectedto a point 42, from which one branch extends to the point 30, andanother branch extends over a 470-ohm resistor 44 to a point 46, fromwhich one circuit branch extends to the gate of the controlled rectifier40. A parallel combination of a 0.022- microfarad capacitor 48 and a30,000-ohm resistor 50 extends between the point 46 and a point 52, fromwhich the circuit continues over a diode 54, which may be of type [N462manufactured by Sylvania Electric Products Inc., of New York, New York,United States of America, and an 820-ohm resistor 56 to a connection toa base reference potential shown in FIG. [as

ground.

The operation of the circuit of FIG. 1 will now be described withreference to the wave forms shown in FIG. 2. These wave forms illustratetransient conditions of voltage and current with respect to time atvarious points in the circuit of FIG. 1, and offer a comparison of thecurrent in the inductive load using the circuit of the presentinvention, as compared to the current in the inductive load using aconventional circuit in which the counter-EMF energy is not capacitivelystored and then used in re-energizing the load.

Initial energization of the inductive load 12 is accomplished by theapplication of a suitable energizing signal S to the terminal 26, whichis associated with the base of the transistor 24, thus causing saidtransistor to conduct, and completing a circuit extending from theterminal 16 over the point 14, the inductive load 12, the point 18, thediode 20, the point 22, and the transistor 24, to ground. When thesignal S is terminated, the

, transistor 24 ceases to conduct, thus interrupting the energizingcircuit. The resulting counter-EMF from the inductive load 12 causes thecapacitor 32 to charge, thus transferring the inductive field energy tocapacitor charge energy. The current path during this transfer of energyextends from the inductive load 12 over the point 18, the diode 20, thepoints 22 and 34, the capacitor 32, the point 30, the diode 28, and backto the inductive load 12. Since the voltage V, at the terminal 38 isequal to the charged capacitor voltage, and since the transistor 24 isnot conducting, the capacitor 32 has no discharge path.

At the time of the next energizing signal S the transistor 24 is oncemore rendered conducting, and the positive terminal of the capacitor 32is grounded. As a consequence, the negative terminal of the capacitor 32is driven below ground, thus causing a negative pulse to be applied tothe cathode of the controlled rectifier 40, causing a gate current tocommence flowing, which in turn causes said controlled rectifier tocommence conducting. A current path is thus established, extending fromthe terminal 16 over the point 14, the inductive load 12, the point 18,the controlled rectifier 40, the points 42 and 30, the capacitor 32, thepoints 34 and 22, and the transistor 24, to ground. Current flow in thispath continues, discharging the capacitor 32 to a point at which theholding current through the controlled rectifier 40 falls offsufficiently to terminate conduction therethrough. The energizingcircuit then extends from the terminal 16 over the point 14, theinductive load 12, the diode 20, the point 22, and the transistor 24 toground, until such time as the energizing signal S is terminated,cutting off the transistor 24.

For given circuit parameters, the size of the capacitor 32 can bedetermined by means of the following equation: a

in which C capacitance of capacitor 32 trmulltor anuatu 1,, current ininductive load 12 L inductance of inductive load 12.

The above equation is derived from the two wellknown energy equations:

These equations can be 'set equal to each other for purposes of derivingthe equation for capacitance,

since the capacitor 32 stores most of the energy which is given up bythe collapsing field of the inductive load 12 W 1 /LC) where:

W time in radians per second L inductance of inductive load 12 Ccapacitance of capacitor 32 and where the inductive load current takesthe form of a second quarter cycle sine wave and the capacitor voltagetakes the form of a first quarter cycle sine wave as shown in FIG. 2.

The same equation may be used to estimate the time required fordelivering the stored energy from the capacitor 32 to the inductive load12 during the energizing cycle, assuming no resistance in the controlledrectifier 40, the capacitor 32, the inductive load 12, and thetransistor 24. In this instance, the inductive load current takes theform of a first quarter cycle sine wave and the capacitor voltage takesthe form of a second quarter cycle sine wave, as shown in FIG. 2.

The diode 20 must have a voltage rating in excess of the voltage levelstored in the capacitor 32 plus the load supply voltage V and must havea current rating dependent upon the duty cycle and current requirementof the inductive load 12. However, the diodes 28 and 40 can be currentsurge rated, since they function only during periods of energy transferbetween the inductive load 12 and the capacitor 32.

The resistor 44 and the diode 54 are used in the gating circuit for thecontrolled rectifier 40 (which also includes the capacitor 48, theresistor 50, and the resistor 56), in order that the gate-to-cathodejunction of the rectifier 40 is not reversed when the cathode is biasedat the V level during charging of the capacitor 32. The resistor 56 andthe capacitor 48 are chosen to supply an exponentially decaying currentpulse to the gate of the rectifier 40 when the negative terminal of thecapacitor 32 is driven negative from ground at the start of theinductive load energization. The maximum gate current equals the storedcapacitor voltage divided by the resistance of the resistor 56.

Where very long periods exist between inductive .load energizing pulses,small leakages in the diode 20 or in the transistor 24 may cause thestored voltage on the capacitor 32 to be reduced. To maintain thestored 1. In combination with an inductive load having a two-terminalwinding, a driving circuit for energizing said winding comprising, incombination,

a direct current voltage supply having two terminals;

means connecting a first one of the terminals of the winding to a firstone of the terminals of the direct current voltage supply;

energy storage means having two terminals;

means including a unidirectional conducting device connecting a firstone of the terminals of the energy storage means to said first terminalof said windmeans including a unidirectional conducting deviceconnecting the second of the terminals of the winding to the secondterminal of the energy storage means; switching means for controllingthe state of energization of the winding, said switching means having afirst terminal connected to said second terminal of said energy storagemeans and a second terminal connected to the second terminal of saiddirect current voltage supply; signal translating means having a firstterminal connected to said second terminal of said winding, a secondterminal connected to said first terminal of said energy storage means,and a control gate;

means for connecting said control gate to said second terminal of saidvoltage supply; and

means for connecting said control gate to said first terminal of saidenergy storage means; whereby deenergization of said winding undercontrol of said switching means causes energy to be stored in saidenergy storage means, and whereby during subsequent re -energization ofsaid winding under control of said switching means the energy stored insaid energy storage means is applied to said winding through said signaltranslating means, which is rendered conducting at such time in responseto the potential level at the first terminal of the energy storagemeans.

2. The combination of claim 1, also including means for applying asource of potential to said second terminal of the energy storage means.

3. The combination of claim 1 wherein the energy storage means comprisesa capacitor.

4. The combination of claim 1 wherein the signal translating meanscomprises a silicon controlled rectifi- 5. The combination of claim 1wherein the means for connecting the control gate to the second terminalof the voltage supply includes a series combination of a resistance, aunidirectional conducting device, and a parallel resistance-capacitancecombination.

6. The combination of claim 1 wherein the means for connecting thecontrol gate to the first terminal of the energy storage means includesa resistance.

7. Drive circuitry for controlling the energization of an inductive loadcomprising, in combination,

switching means for controlling the energization and deenergization ofthe inductive load;

energy storage means capable of storing'the energy produced bydeenergization of the inductive load; first circuit means to apply theenergy produced by deenergization of the inductive load to the energysto age eans; signa t ans atmg means having a first terminal contheinductive load to aid in the re-energization.

thereof when the switching means is operated to energize the inductiveload.

8. The drive circuitry of claim 7 in which the energy storage meanscomprises a capacitor.

9. The drive circuitry of claim 7 in which charging means are providedfor maintaining the energy storage means in a fully charged conditionduring the period when the inductive load is deenergized.

10. The drive circuitry of claim 7 in which the signal translating meansis a silicon controlled rectifier.

1. In combination with an inductive load having a two-terminal winding,a driving circuit for energizing said winding comprising, incombination, a direct current voltage supply having two terminals; meansconnecting a first one of the terminals of the winding to a first one ofthe terminals of the direct current voltage supply; energy storage meanshaving two terminals; means including a unidirectional conducting deviceconnecting a first one of the terminals of the energy storage means tosaid first terminal of said winding; means including a unidirectionalconducting device connecting the second of the terminals of the windingto the second terminal of the energy storage means; switching means forcontrolling the state of energization of the winding, said switchingmeans having a first terminal connected to said second terminal of saidenergy storage means and a second terminal connected to the secondterminal of said direct current voltage supply; signal translating meanshaving a first terminal connected to said second terminal of saidwinding, a second terminal connected to said first terminal of saidenergy storage means, and a control gate; means for connecting saidcontrol gate to said second terminal of said voltage supply; and meansfor connecting said control gate to said first terminal of said energystorage means; whereby deenergization of said winding under control ofsaid switching means causes energy to be stored in said energy storagemeans, and whereby during subsequent re-energization of said windingunder control of said switching means the energy stored in said energystorage means is applied to said winding through said signal translatingmeans, which is rendered conducting at such time in response to thepotential level at the first terminal of the energy storage means. 2.The combination of claim 1, also including means for applying a sourceof potential to said second terminal of the energy storage means.
 3. Thecombination of claim 1 wherein the energy storage means comprises acapacitor.
 4. The combination of claim 1 wherein the signal translatingmeans comprises a silicon controlled rectifier.
 5. The combination ofclaim 1 wherein the means for connecting the control gate to the secondterminal of the voltage supply includes a series combination of aresistance, a unidirectional conducting device, and a parallelresistance-capacitance combination.
 6. The combination of claim 1wherein the means for connecting the control gate to the first terminalof the energy storage means includes a resistance.
 7. Drive circuitryfor controlling the energization of an inductive load comprising, incombination, switching means for controlling the energization anddeenergization of the inductive load; energy storage means capable ofstoring the energy produced by deenergization of the inductive load;first circuit means to apply the energy produced by deenergization ofthe inductive load to the energy storage means; signal translating meanshaving a first terminal connected to one side of the load, a secondterminal connected to one side of the energy storage means, and acontrol gate connected to a reference potential; second circuit meansincluding the second terminal and control gate of the signal translatingmeans, whereby the conductivity of the signal translating means iscontrolled by the energy storage condition of the energy storage means;and third circuit means associated with the switching means, the energystorage means, the signal translating means, and the inductive load forapplying the energy stored in the energy storage means to the inductiveload to aid in the re-energization thereof when the switching means isoperated to energize the inductive load.
 8. The drive circuitry of claim7 in which the energy storage means comprises a capacitor.
 9. The drivecircuitry of claim 7 in which charging means are provided formaintaining the energy storage means in a fully charged condition duringthe period when the inductive load is deenergized.
 10. The drivecircuitry of claim 7 in which the signal translating means is a siliconcontrolled rectifier.